Guide to parameters

Although many of the parameters in the params.txt file are self explanatory and commented, this page aims to provide a description of the key parameters for GRFolres.

The GRChombo parameter guide can be found here, which will cover the majority of the variables.

Guide to specific parameters

For the purposes of this page, we will refer to the params.txt in the current binary black hole example.

Modified puncture gauge

• a0 is the value of the $a(x)$ function, which we set to be a constant.
• b0 is the value of the $b(x)$ function, which we set to be a constant.

Coupling and potential

• lambda_GB is the coupling constant in the Gauss-Bonnet coupling $f(\phi)$.
• cutoff_GB is the value of $r_0$ or $\chi_0$ for the excision of the Gauss-Bonnet terms.
• factor_GB $=\tau$ is the parameter in the excision function.
• g2is the value of the $g_2(\phi)$ coupling, which we set to be a constant.